The present invention is a continuing application of the eight-stroke internal combustion engine, which was filed as U.S. Pat. No. 6,918,358 (application Ser. No. 10/619,147), and the engine of this type can also be abbreviated as the eight-stroke engine.
The original design of the eight-stroke engine suffers from low fuel efficiency in heavy load due to the backfiring effect in the coordinate-port before the slave piston has moved to the TDC of the slave-compression-stroke, this causes extremely high heat loss through the coordinate-port and may damage valve body; as this backfiring effect is undesired, several attempts with current variable valve timing mechanisms has been experimented but the actuation-timing of the coordinate valve requires a complex computation of the comparison between the master cylinder combustion pressure and the slave cylinder compression pressure and other environment factors during operation, and the open-time is too short for the mechanically controlled variable-valve-timing to perform correctly in the high speed application, therefore a new solution is required.
According to the concept of the eight-stroke-operation, after the high-density-air (which is also referred as the compressed air from the slave cylinder) of the coordinate-port is injected into the master cylinder, the combustion medium of the master cylinder will come into contact with more oxygen, thereby speeding up the combustion reaction of the carbon monoxide into the carbon dioxide, which will increase the overall pressure in the master cylinder (this process is referred to as the second combustion in the previous eight-stroke engine patent application); if the air flows between the master cylinder and the slave cylinder are correctly regulated as in the theory of the eight-stroke-operation, the fuel efficiency can be over 35% for gasoline type eight-stroke engine and 45% for the diesel type eight-stroke engine (small vehicle applications).
To conclude with the experiment data of the eight-stroke engine prototype, it is found that the valve timing of coordinate-port is extremely difficult to control in high rpm operation with a load change (sudden load increase or load decrease); thus this is the main objective to overcome the above-mentioned technical difficulty.